Conventionally, toothed belts have been used for power transmission in internal combustion engines and the like. To improve the wear resistance of a toothed belt, a facing fabric is adhered to a tooth surface of the belt. The facing fabric is subjected to impregnation treatment with a treatment agent such as RFL or rubber cement.
Recently, toothed belts have been increasingly used under high-temperature and high-load conditions. That is, the use of more compact engine compartments or the like requires toothed belts to be miniaturized and functional in higher temperature environments. Moreover, toothed belts have been finding wider applications, and may be used in the presence of oil in some cases.
When a toothed belt is used in a high-temperature and high-load environment, however, a facing fabric treatment agent such as RFL can wear away rapidly. For this reason, cracks and the like are more likely to occur in the facing fabric, and the lifetime of the toothed belt may be shortened. Moreover, since the above-described facing fabric treatment agent does not have sufficient oil resistance, the toothed belt tends to have a reduced lifetime when used in the presence of an oil environment.
Patent Document 1 discloses that a facing fabric is subjected to RFL treatment, and then further subjected to impregnation treatment with rubber cement to which an epoxy compound or the like is added.
In addition, technologies for improving the durability of a belt by preventing the degradation of a facing fabric by treating it with RFL or rubber cement have been widely known for some time. However, when the belt is operated in the presence of oil or water, or under high-temperature conditions, treatment agents such as RFL and rubber cement are prone to degradation and cannot protect the facing fabric sufficiently. For this reason, the treatment agent applied to the facing fabric wears away rapidly, and pulleys come in direct contact with the fiber material of the facing fabric. As a result, cracks and the like occur in the facing fabric, and the durability of the belt is compromised.
For example, a scheme is also known in which the tensile strength of a facing fabric is improved by adding an aromatic epoxy resin to an RFL treatment liquid, as disclosed in Patent Document 2.
Patent Document 1: Japanese Patent Application Publication No. 2004-324832.
Patent Document 2: Japanese Patent Application Publication No. 2001-220008.